6.35mm TRS
The 6.35mm TRS (tip-ring-sleeve), also known as a 1/4-inch phone jack or quarter-inch jack, is a standard audio connector widely used for headphone outputs on professional broadcast and video equipment. The three-conductor TRS configuration carries a stereo signal (left on tip, right on ring, ground on sleeve) or can be used for balanced mono audio.
On professional VTRs and broadcast equipment, 6.35mm TRS jacks are most commonly found as front-panel headphone monitoring outputs, allowing operators to monitor audio during recording, playback, and editing operations.